1. Field of the Invention
The present invention relates to a display apparatus including an array of pixels each including a light emitting element, and more particularly, to an active matrix display apparatus adapted to control currents flowing through light emitting elements, for example, of the organic electroluminescent type by using insulating gate field effect transistors disposed in the respective pixels. The present invention also relates to a method of driving such a display apparatus and to an electronic device using such a display apparatus.
2. Description of the Related Art
In an image display apparatus such as a liquid crystal display, a large number of liquid crystal pixels are arranged in the form of a matrix and the intensity of light transmitting through or reflected from the respective pixels are controlled in accordance with image information thereby displaying an image. Organic electroluminescent elements may be used as light emitting elements disposed in the respective pixels. In contrast to liquid crystal pixels which are not of the self-luminous type, the organic electroluminescent display is of the self-luminous type and has the following advantages. That is, the organic electroluminescent display provides high visibility compared with the liquid crystal display, does not need backlighting, and can respond at a high speed. The intensity levels (gray-scale levels) of each light emitting element can be controlled by controlling the current flowing through the light emitting element. That is, the organic electroluminescent display device is of the current-controlled type. In this respect, the organic electroluminescent device is very different from the liquid crystal display which is of the voltage-controlled type.
As with the liquid crystal display, the organic electroluminescent display can be driven by a passive matrix addressing scheme or an active matrix addressing scheme. Although the passive matrix address scheme needs a simpler configuration, the disadvantage of this scheme is that it is difficult to realize a large-size high-resolution display. For the above reason, the active matrix address scheme is currently receiving more attention. In this scheme, the current flowing through the light emitting element disposed in each pixel is controlled by an active element (for example, a thin-film transistor (TFT)) disposed in each pixel. Further detailed descriptions of this scheme and associated techniques may be found, for example, in patent documents listed below.
Japanese Unexamined Patent Application Publication No. 2003-255856
Japanese Unexamined Patent Application Publication No. 2003-271095
Japanese Unexamined Patent Application Publication No. 2004-133240
Japanese Unexamined Patent Application Publication No. 2004-029791
Japanese Unexamined Patent Application Publication No. 2004-093682
Japanese Unexamined Patent Application Publication No. 2006-215213